Preheat the oven to 200°C/fan 180°C/gas mark 6. Bring a pan of water to the boil and cook the potatoes for 10 minutes until tender. Drain thoroughly, then toss with 2 tbsp olive oil, the thyme and 3 garlic cloves, which should be lightly bashed beforehand. Season, then put in a roasting tin and cook in the oven for 30-35 minutes, shaking the tray occasionally.
Meanwhile, heat the remaining oil in a large, lidded saucepan or casserole dish. Add the shallots and cook for 2-3 minutes until beginning to soften. Crush the remaining garlic clove, then add to the pan and cook for another minute. Add the chicken and cook for 4-5 minutes, turning occasionally until brown all over.
Pour in the cider and bubble for a minute, before adding the stock. Cover with the lid and simmer for 30 minutes. Remove the lid and cook for another 12-15 minutes until the sauce has reduced slightly, and the chicken is tender and cooked through. Add the green beans to a pan of boiling water for the final 3-4 minutes. Drain thoroughly.
Stir the crème fraîche and mustard through the chicken and finish with a scattering of parsley. Serve with the green beans and potatoes on the side.